使用GetElementById单击WebView中的Button

Question

i want to click a button in webview by get element . and also i want use it in a service . i write this code . but its not work.

public class MyService extends Service {
public MyService() {
}

@Override
public IBinder onBind(Intent intent) {
    throw new UnsupportedOperationException("Not yet implemented");
}

@RequiresApi(api = Build.VERSION_CODES.KITKAT)
@Override
public void onCreate() {
    super.onCreate();
    final WebView[] wv = {new WebView(MyService.this)};
    wv[0].getSettings().setJavaScriptEnabled(true);
    wv[0].getSettings().setSupportMultipleWindows(true);
    wv[0].getSettings().setAppCacheEnabled(false);
    wv[0].setWebViewClient(new WebViewClient() {
        @Override
        public boolean shouldOverrideUrlLoading(WebView view, String url) {
            return false;
        }
    });


    wv[0].addJavascriptInterface(new Object() {
        @JavascriptInterface
        public void test() {

        }
    }, "test");


    wv[0].setWebChromeClient(new WebChromeClient() {
        @Override
        public boolean onCreateWindow(WebView view, boolean isDialog, boolean isUserGesture, Message resultMsg) {
            return true;
        }
    });
    wv[0].getSettings().setUserAgentString("Mozilla/4.0 (compatible; MSIE 5.01; Windows NT 5.0)");
    wv[0].loadUrl("http://example-site.com");
    Handler handler = new Handler();
    handler.postDelayed(new Runnable() {
        @Override
        public void run() {
            wv[0].evaluateJavascript("document.getElementsById('my_button')[0].click();", null);
        }
    }, 25000);
}

}

i use a timer for load . its 25 s. please help for solve this problem